Move the Tobin Bridge and NE Expressway to west Chelsea and Sullivan Square.

A relocated Rutherford Ave would take traffic from the new Tobin Bridge that is bound for Storrow Drive or the North Station area. The existing Rutherford Ave would be converted into a much narrower landscaped surface street.

The current Tobin Bridge and NE Expressway would be replaced by a light rail line. A high-level bridge would be built where the current Tobin Bridge is located, to serve local and pedestrian traffic between Chelsea and Charlestown, and the new light rail line.

I had the exact same idea a while ago, except with the new NE Expressway slightly further north paralleling the rail line for some better curves on the interchange. This would also allow a full interchange with Route 16 and 99 to alleviate some of that traffic.

I don't see the need for a high level bridge to reconnect Broadway, a draw would be much better for pedestrians, bikers and the surrounding environment.

As for Rutherford, I think a bypass is unnecessary. Most of the traffic there is induced demand from people skirting the toll on the Tobin and local traffic. It's made a million times worse by the traffic from the demolished overpass and half the closed underpass all cramming though the Rotary with no design changes made. Honestly a wholesale downgrading of Rutherford with better highway connectivity onto a new Tobin alongside the current Sullivan Square plans should be just fine.

The core idea of moving Rt 1 into the industrial wasteland to allow better connectivity between Chelsea and Charlestown is great though. I feel like a push to do this should start now, so when the Tobin's life expectancy is up something would already be in the works.

When I proposed this last I believe someone said the capacity on 93 north of the current NE Expressway interchange is substandard to handle the additional traffic, so bear in mind this would probably have to go alongside a widening of 93 through Somerville. And since it can't really get much wider, you're looking at another highway burying project. You would also have to reconfigure / rebuild the ramps from 93 onto Mem Drive and Storrow I believe. Not a bad thing, but an expensive one.